Composites were ruled out more than thirty years ago as a means of enhancing the figure-of-merit, and therefore conversion efficiency, of thermoelectric materials. However, recently it has been experimentally proven that the shortcomings of composite thermoelectric materials can be overcome using nanostructured secondary phases. Phase change materials, which have found applications in nonvolatile memory storage, have been identified as an alternative to Pb-based chalcogenide thermoelectric materials. Research has revealed that the thermoelectric figure-of-merit for these compounds can be increased using secondary phases in the absence of nanostructuring. The following work has studied the effects of secondary phases of Sb on the thermoelectric properties of Ge17Sb2Te20. This work has found that secondary phases of elemental Sb introduce additional charge carrier scattering that leads to increased power factor values and figure-of-merit values in excess of a factor of 2, further emphasizing the importance of revisiting composites for enhancing the performance of thermoelectric materials.